Anyone who thinks they know the definition is wrong.
The term is a legal term, and a political term.
It changes each time you change jurisdictions where it is used.
Even within a jurisidiction the tame changes as case law modifies it, and as new legislation expands the definition.
The definition has changed many times in California for example.
This can be an assault weapon some places:
Even a single shot in.50 BMG is held to assault weapon legislation in California.
The federal definition no longer exists because the legislation that defined it is no longer current.
Most proposed reinstatements include just a single line that would greatly expand the definition.
Like allowing the attorney general to name anything an assault weapon.
Or reduce the number of allowable "evil" features from 2 to 1.
It is currently undefined at the federal level and is defined differently in various states and locales.